1. Field of the Invention
This invention relates to a technique for a resistive RAM (RRAM), and more particularly to a RRAM and a method of manufacturing the same.
2. Description of Related Art
In general, an RRAM includes a transition metal oxide (TMO), a top electrode (TE) and a bottom electrode (BE), and is connected to the outside via a top wire and a bottom wire. The RRAM switches a resistance state from 0 to 1 or from 1 to 0 by means of an external operating voltage/current. Since the conductive path is controlled by means of oxygen vacancies under a low resistance state (LRS), once oxygen ions diffuse into a TMO layer due to high temperature, the oxygen vacancies inside the conductive path would be reduced, so that operation of the RRAM becomes unstable.
Therefore, there have been a variety of techniques for reducing diffusion of the oxygen ions into the TMO, such as increasing a Set power, which, however, affects the yield for Reset. Moreover, there is a technique of using an oxide layer to block the diffusion of the oxygen ions, but it may impact on the conductivity of the memory as a whole.
Among various RRAMs, an RRAM having hafnium oxide as the TMO layer receives much attention due to excellent durability and high switching speed. However, it is often hard to retain a Ti/HfO2 RRAM currently employed in LRS in high temperature, leading to deterioration in the so-called “high-temperature data retention” (HTDR). Thus, there is necessity for research and improvement in the RRAM.